As a display for large, thin TV sets, a plasma display has attracted greater attention. FIG. 5 schematically shows an oblique perspective view of a structure of a pixel in a plasma display. In the example given in FIG. 5, a glass substrate 12 in the front plate 18 that serves as a display screen carries two or more pairs of a sustain electrode 14 and a scan electrode 13 that are produced from silver, chromium, aluminum, nickel, etc., and aligned to form stripes with their length direction coinciding with the longitudinal direction of a display region in which the longitudinal and transverse directions are parallel to the short and long sides of the display region. A black stripe 15 that serves to maintain contrast in a displayed image may be provided between the pixels in the longitudinal direction of the plasma display. The sustain electrode 14 and scan electrode 13 are clad in a 20 to 50 μm thick glass-based dielectric layer 16 that is coated with a protection layer 17.
In the glass substrate 19 in the rear plate 25, on the other hand, two or more address electrodes 20 are provided to form stripes with their length direction coinciding with the longitudinal direction, and the address electrodes 20 are clad in a glass-based dielectric layer 21. A main barrier rib 22 and an auxiliary barrier rib 23 are formed on the dielectric layer 21 to separate discharge cells, and a phosphor layer 24 is provided in a discharge space formed by the barrier ribs and dielectric layer 21. For a full-color plasma display, the phosphor layer consists of materials that emit red (R), green (G), or blue (B) light. The front plate and the rear plate are sealed in such a way that the sustain electrode 14 in the front plate 18 extends perpendicular to the address electrode 20 in the rear plate 25, and rare gas such as helium, neon, and xenon fills the gap between these substrates to form a plasma display. Each pixel is formed with its center at the intersection of the scan electrode 13 and the address electrode 20, and the plasma display has two or more pixels to display an image.
When an image is produced in a plasma display, a voltage larger than the breakdown voltage is applied to the luminescence-free space between the scan electrode 13 and the address electrode 20 in a selected pixel, producing cations and electrons through ionization. Since the pixel is a capacitative load, they move through the discharge space toward the electrode with the opposite polarity, resulting in electrification on the inner wall of the protection layer 17. Since the protection layer 17 has a high resistance, the electric charge on the inner wall will be retained as wall charge.
Then, a self-sustaining discharge voltage is applied between the scan electrode 13 and the sustain electrode 14. If wall charge exists, electrical discharge can take place at a voltage lower than the breakdown voltage. Electrical discharge excites xenon gas in the discharge space to generate 147 nm ultraviolet ray, and this ultraviolet ray in turn excites the phosphor layer 24 to cause luminescence to produce an image.
In a known method to form an address electrode, dielectric layer, barrier rib, and phosphor layer to constitute the rear plate of a plasma display, a substrate is coated or laminated with a photosensitive paste, and then exposed to light through an appropriate pattern, followed by development with an appropriate developer.
In a proposed method (Patent Literature 1), for instance, a photosensitive paste layer consisting of ceramic powder and ultraviolet curable resin is formed over a substrate and exposed to light through a photomask with an appropriate pattern, followed by development and calcination.
However, when a barrier rib grid comprising main barrier ribs and auxiliary barrier ribs is formed by grid-like patterning and calcination of a paste coating layer composed of ceramic powder and resin, bulged portions will be produced at the intersections of the main barrier ribs and the auxiliary barrier ribs, while the front plate and the barrier ribs will not come in contact in the other portions, leading to undesired discharge.
The above method has a problem because if foreign matters or flaws exist on the photo mask, the patterns obtained after exposure and development will mostly contain defects such as disconnections and unintended connections to lower the yield.
As a method for solving the problem; it is proposed to prepare a photo mask with an opening length kept shorter than that of the pattern layer and carry out exposure while moving the substrate or photo mask (Patent Literatures 2 and 3). However, when a complicated pattern, such as for grid-like barrier ribs of a plasma display panel, some barrier ribs at the end of the moving path of the substrate will tend to fail to be produced properly, leading to problems such as a decrease in productivity or a decline in the quality of the resulting display panel.
Patent Literature 1: JP 2-165538 A
Patent Literature 2: JP 2004-240095 A
Patent Literature 3: WO 2006/025266 A1